1. Field of the Invention
The present invention generally relates to a surface profilometer and, more particularly, to a tilting adjustable surface profilometer capable of obtaining a surface profile with an omni-directional angle of a sample.
2. Description of the Prior Art
High-precision surface profilometry is a key technique in the modern world. With the downsizing of the components, precise and reliable detection skills on surface profilometry are required to verify the size of microstructures and precision of surface profiles to certificate the manufacture quality.
Optical non-contact detection is widely used in various industries such as brightness enhancement films (BEF's) for liquid-crystal display (LCD's) to acquire the precise surface profile of a sample without any damage to the sample. The BEF's are detected using a surface profilometer to verify whether the surface microstructure meets all the requirements for the LCD's using the BEF's to exhibit enough brightness.
Please refer to FIG. 1, which is a schematic diagram wherein the reflected light cannot return back to the optical microscope. As the surface gradient of the sample is large, especially when co-axial light is used to pass through the optical microscope 11, the reflected light 13 from the sample 12 can not return to the optical microscope 11. Therefore, it is impossible to obtain the surface profile of the sample. Under such circumstances, interpolation is used. However, the acquired result is far from satisfactory compared to the actual surface profile.
In the literature, there are some reports and patents presented to overcome the afore-mentioned problems. However, they are not suitable for measuring the micro-structured surface profile of a large sample.
Please refer to FIG. 2, which is a structural diagram of a conventional 3-D surface profilometer. In the surface profilometer 21, the sample 23 is fixedly disposed perpendicular to the optic axis 22 so that reflected light from the sample 23 cannot be collected when the surface gradient is large, as shown in FIG. 3. Meanwhile, image interpolation is required to cause distortion compared to the actual surface profile.
Please refer to FIG. 4, which is a schematic diagram showing a disclosure of TW Patent No. I229186. In FIG. 4, two linear scanning devices 21, 22 with different view angles are used with a tilt light source 23 to roughly detect the size and shape of a sample. It is useful for defect detection on a large area. However, it is not suitable for 3-D surface profilometry. Moreover, when the surface gradient of the sample is large, the reflected surface signal cannot be received.
Please refer to FIG. 5, which is a schematic diagram showing a disclosure of U.S. Pat. No. 6,449,048. In FIG. 5, an interferometer is tilt an angle relative to a sample. A conventional vertical scanning interferometer (VSI) and a phase-shift interferometer (PSI) are used to continuously scan to surface of the sample so as to obtain the surface profile of the sample without image interpolation. However, a surface profile with an omni-directional angle cannot be obtained when the surface gradient of the sample is large.
Please refer to FIG. 6, which shows a disclosure of QED Technology for surface profilometry on a large-area tilt and rotating sample. In FIG. 6, a surface profile of a large-area sample with a large surface gradient is obtained by tilting and rotating the sample. A surface profilometer is used to obtain the surface profile of the large sample with a large surface gradient. Even though this method overcomes the problems resulting from the previous disclosures, it can only be used to detect a small-size sample. If the sample is a roller mold for manufacturing BEF's for LCD's, which is hard to be rotated and tilt, detection thereon cannot be performed.